148 
Fishery Bulletin 1 10(2) 
points under the re-immigration model, compared with 
190 of 1079 data points for the CJS model, translating 
to a mean squared predicted error of 0.04 and 0.18 re- 
spectively. For ATI whales, there were 25 discrepancies 
from 569 data points under the re-immigration model, 
compared with 91 in 569 for the CJS model, correspond- 
ing to MSPEs of 0.04 and 0.16, respectively. Inference 
was therefore based on parameter estimates from the 
flexible emigration-re-immigration model, which in- 
dicated notable differences in the fidelity of the two 
populations to the study area (Table 1). 
GOA transients showed a much higher rate of ex- 
change of individuals in the study area, with a rela- 
tively high probability of emigration (posterior median 
p A =0.55) and low rate of re-immigration (p K '=0.17), 
compared to a low rate of emigration and high rate 
of re-immigration for the ATI population (p A =0.08, 
p K '=0.77), implying high study area fidelity for the 
ATI whales. Similarly, the average 
probability of capture was higher 
for AT1 (/j b = 0.98) compared with 
GOA (jU® = 0.83) individuals, imply- 
ing that almost all of the ATI in- 
dividuals in the study area were 
photographed in each year, likely 
because of a higher fidelity to the 
study area and smaller range. Al- 
though the average apparent sur- 
vival was high for both populations 
(GOA ^=0.98; ATI /i*=0.99), there 
were noticeable annual deviations 
from the average (Fig. 4). Although 
there was a substantial dip in the 
GOA transients’ apparent survival 
in one year, 1986, there was a con- 
sistent trend in the ATI population, 
with survival from 1989 to 1990 
showing a marked decrease (poste- 
rior median = 0.68, 95% probability 
interval = 0.48 to 0.86) compared 
with the overall average, with no 
overlap in 95% probability intervals 
between this estimate and those for 
most other years. 
The trends in abundance of the 
two populations, based on estimates 
of abundance and parameters of the 
20 
Number of years seen 
Figure 3 
Frequency plot of the number of individual whales photographed in different 
numbers of annual sampling periods, for both the ATI and Gulf of Alaska 
(GOA) transient killer whale (Orcinus orca) populations. 
Table 1 
Fit of photographic identification data to the mark-recapture model with emigration and re-immigration, for both ATI and Gulf of 
Alaska (GOA) transient killer whale ( Orcinus orca) populations. l=the probability that an individual in the study area migrates 
out of it each year; v=the probability that an individual not in the study area population migrates back into it each year; 0=the 
annual probability of survival, G5=the annual probability of capture (identification) in the study area. Estimates are presented 
as the 0.025,0.50, and 0.975 probability intervals of the posterior probability distribution (i.e., median surrounded by 95% prob- 
ability intervals) for the average (p) value across May-September periods, plus the probability of between-year differences in 
parameters over the 27 time periods, given by the posterior probability p(g= 1) of each respective time-varying indicator variable 
g. Additionally, the parameter /3j is included to indicate the magnitude and direction of abundance trend (on the log scale). 
Posterior estimates 
Population 
Emigration 
ft [p(g A =D] 
Re-immigration 
g K lp(g K = D) 
Survival 
ft [p(ft=l)] 
Capture 
ft [p(g w = D] 
Trend 
ft [p(ft=l>l 
GOA 
0.21,0.55,0.80 
[1.00] 
0.02,0.17,0.67 
[1.00] 
0.94,0.98,0.99 
[ 1 . 00 ] 
0.55,0.83,0.99 
[1.00] 
-1.2,04,1.3 
[0.02] 
ATI 
0.02,0.08,0.23 
[1.00] 
0.18,0.77,0.97 
[0.71] 
0.96,0.99,1.00 
[1.00] 
0.92,0.98,1.00 
[0.64] 
-1.1, -0.8, -0.5 
[1.00] 
